Rotary heat exchangers

ABSTRACT

To reduce the friction between the matrix of a rotary ceramic heat-exchanger and a counterface seal, the matrix core is impregnated with a metallic salt and this treatment is followed by decomposition of the salt to the oxide. The preferred metal oxides are chromium oxide, cobalt oxide and zinc oxide in quantities in the range of 2 to 10 percent of the weight of the matrix core.

United States Patent [1 1 ONeill et a1.

45] July 2,1974

ROTARY HEAT EXCHANGERS Inventors: John Sidney ONeill, Alcester; Alan John Surrall, Studley; Calvin Eric Silverstone, Alcester, all of England Assignee: British Leyland Truck and Bus Division Limited, Leyland, Lancashire, England Filed: June 21, 1972 Appl. No.: 264,922

Foreign Application Priority Data July 3, l97l Great Britain 31254/7] Sept. 9, 1971 Great Britain 42005/71 US. Cl 165/10, 165/9, 277/96 R, ll7/ll3,ll7/l69,R Int. Cl. F28d 19/00 Field of Search 165/9, l0; 277/96 R;

[5 6] References Cited UNITED STATES PATENTS 3,576,208 4/l97l Cassidy [65/9 FOREIGN PATENTS OR APPLICATIONS 1,242,987 8/1971 Great Britain 165/9 Primary ExaminerAlbert W. Davis, Jr. Attorney, Agent, or Firm-Brisebois & Kruger 15 Claims, No Drawings This invention relates to rotary heat-exchangers of the kind having a rotary disc-type matrix which comprises a foraminous core of ceramic glass-ceramic material formed with a multitude of open-ended, thinwalled passages lying substantially parallel to its rotational axis.

Heat-exchangers of the kind referred to are employed in gas turbine power plants to extract heat from the exhaust gases, and to transfer it to the compressed intake-air before this enters the combustion chamber of the gas turbine engine. It is, of course, necessary to segregate the two gaseous heat-exchanging fluids at all times, and to minimize leakage between the highpressure zone, occupied by the compressed intake-air, and the low-pressure zone occupied by the exhaust gases. To this end, it is common practice to employ seals which make rubbing contact with the corresponding face of the matrix. The power required to drive the heat-exchanger disc, and the wear rate of the seals, is largely function of the seal loading and the coefficient of friction between the seal and the disc.

The purpose of the present invention is to reduce the coefficient of friction of the above-mentioned ceramic or glass-ceramic core. This is achieved, according to the invention, by impregnating the matrix core with a metallic salt, followed by decomposition of the salt to the oxide. Preferably, the metal oxide is chromium oxide or cobalt oxide or zinc oxide and in a quantity in the range of 2 to percent of the weight of the matrix core to be impregnated.

In a convenient and efficient manner of carrying the invention into effect, the matrix core is boiled in an aqueous solution of the metallic salt and then slowly cooled to room temperature, at which it is allowed to soak for at least one hour, followed by a subsequent heating in air to a temperature within the range of 300 C. to about 800 C., dependent on the salt used, in order to decompose the salt to the oxide. For example, when the metallic salt employed for impregnating the matrix core is either chromium nitrate or cobalt nitrate the above-mentioned subsequent heating of the matrix core in air is carried out within the temperature range 400-500 C. And when the metallic salt employed is zinc nitrate the relevant temperature range for the subsequent heating of the matrix core in air is 300-400 C.

We claim: a

l. A method of reducing the coefficient of friction of 2 pregnated.

3. A method according to claim 1, in which the oxide is cobalt oxide and in a quantity in the range of 2 to 10 percent of the weight of the matrix core to be impregnated.

4. A method according to claim 1, in which the oxide is zinc oxide and in a quantity in the range of 2 to 10 percent of the weight of the matrix core to be impregnated.

5. A method according to claim 1, in which the matrix core is boiled in an aqueous solution of the metallic salt and then slowly cooled to room temperature, at which it is allowed to soak for at least one hour, followed by a subsequent heating in air to a temperature within the range of 300 C. to about 800 C. in order to decompose the salt to the oxide.

6. A method according to claim 5, in which the salt is chromium nitrate and the subsequent heating of the matrix core in air is effected within the temperature range 400500 C.

7. A method according to claim 3, in which the salt is cobalt nitrate and the subsequent heating of the matrix core in air is effected within the temperature range 400-500 C.

8. A method according to claims, in which the salt is zinc nitrate and the subsequent heating of the matrix core in air is effected within the temperature range 300400 C. 9. A method of reducing the coefficient of friction of a foraminous ceramic matrix core of a rotary heat exchanger which comprises impregnating the ceramic material of thematrix core with a solution of a chromium salt, followed by decomposition of the salt to the oxide.

10. A method according to claim 9, in which the oxide is chromium oxide and in a quantity in the range of 2 to 10 percent of the weight of the matrix core to be impregnated.

11. A method according to claim 9, in which the matrix core is boiled in an aqueous solution of the chromium salt and then slowly cooled to room temperature, at which it is allowed to soak for at least one hour, followed by a subsequent heating in air to a temperature wihin the range of 400 to 500 C in order to decompose the salt to the oxide.

12. A method according to claim 11 in which the chromium salt is chromium nitrate.

13. A foraminous ceramic matrix regenerator core, the ceramic material of which'core isimpregnated with a metallic oxide which reduces the coefficient of friction of the core without obstructing the passages therein.

14. A rotary regenerator comprising a core as claimed in claim 13.

15. A core as claimed in claim 13 in which said oxide is a chromium oxide. 

2. A method according to claim 1, in which the oxide is chromium oxide and in a quantity in the range of 2 to 10 percent of the weight of the matrix core to be impregnated.
 3. A method according to claim 1, in which the oxide is cobalt oxide and in a quantity in the range of 2 to 10 percent of the weight of the matrix core to be impregnated.
 4. A method according to claim 1, in which the oxide is zinc oxide and in a quantity in the range of 2 to 10 percent of the weight of the matrix core to be impregnated.
 5. A method according to claim 1, in which the matrix core is boiled in an aqueous solution of the metallic salt and then slowly cooled to room temperature, at which it is allowed to soak for at least one hour, followed by a subsequent heating in air to a temperature within the range of 300* C. to about 800* C. in order to decompose the salt to the oxide.
 6. A method according to claim 5, in which the salt is chromium nitrate and the subsequent heating of the matrix core in air is effected within the temperature range 400*-500* C.
 7. A method according to claim 3, in which the salt is cobalt nitrate and the subsequent heating of the matrix core in air is effected within the temperature range 400*-500* C.
 8. A method according to claim 5, in which the salt is zinc nitrate and the subsequent heating of the matrix core in air is effected within the temperature range 300* -400* C.
 9. A method of reducing the coefficient of friction of a foraminous ceramic matrix core of a rotary heat exchanger which comprises impregnating the ceramic material of the matrix core with a solution of a chromium salt, followed by decomposition of the salt to the oxide.
 10. A method according to claim 9, in which the oxide is chromium oxide and in a quantity in the range of 2 to 10 percent of the weight of the matrix core to be impregnated.
 11. A method according to claim 9, in which the matrix core is boiled in an aqueous solution of the chromium salt and then slowly cooled to room temperature, at which it is allowed to soak for at least one hour, followed by a subsequent heating in air to a temperature wihin the range of 400* to 500* C in order to decompose the salt to the oxide.
 12. A method according to claim 11 in which the chromium salt is chromium nitrate.
 13. A foraminous ceramic matrix regenerator core, the ceramic material of which core is impregnated with a metallic oxide which reduces the coefficient of friction of the core without obstructing the passages therein.
 14. A rotary regenerator comprising a core as claimed in claim
 13. 15. A core as claimed in claim 13 in which said oxide is a chromium oxide. 